Field of the Invention
The present invention relates to a charging device of a welding fixture of spacer grid.
Description of the Related Art
Generally, a nuclear reactor is equipment that is made to control nuclear fission artificially to generate heat, or to be used for various purposes such as production of radioisotope or plutonium, or radiation filed formation, etc.
In general, light water reactor nuclear power plant uses enriched uranium in which ratio of uranium-235 is increased by 2 to 5%. For nuclear fuel to be used in nuclear reactors, fuel fabrication is processed in such a way that cylindrical pellet hefting about 5 g is made of uranium. In order to manufacture a fuel rod, these pellets come charging zircaloy cladding and spring and helium gas are put in and then an end plug is welded in a rod end. The fuel rods are charged in skeleton finally to form a fuel assembly and combusted by nuclear reaction in the nuclear reactor.
Spacer grid in nuclear fuel assembly which forms skeleton with a fuel rod, instrument tube, and guide tube, is made by dozens of spacer grid straps. Each spacer grid strap has a plurality of incision parts such as a slot. Spacer girds are placed longitudinally and laterally at regular interval so that spacer grids cross each other respectively. Thus incision parts are interconnected to each other by fitting to each other so that spacer grid forms grid space.
However these spacer grid straps are interconnected to each other by inserting into incision parts, spacer grid itself sways because of gaps in most incision parts. Thus the points of intersection where spacer grids cross each other, and parts in which connection is not solid such as outside, corner, etc. are welded in order to prevent spacer grids from swaying. Laser welding is mostly used for the welding method of spacer grid.
For example, the present applicant's Korean Patent No. 10-0922162 (registered on 9 Oct. 2009) suggests a laser welding device for spacer grid of nuclear fuel assembly for enhancing workability and productivity.
In the laser welding device for spacer grid, spacer grid straps before welding are temporarily assembled and then are assembled with a welding fixture comprising a plurality of lateral plates, upper and lower support plates in order to be supported, and then welding is operated.
As another embodiment, the present applicant's Korean Patent No. 10-0952183 (registered on 2 Apr. 2010) suggests an apparatus for loading and unloading automatically welding fixture to charge a welding fixture into a welding chamber and withdraw a welded spacer grid automatically.